GENERAL GYNECOLOGY

The study of laparoscopic electrosurgical instruments on thermaleffect of uterine tissues

Qian Zhu • Jiaying Ruan • Li Zhang •

Wei Jiang • Hongqian Liu • Gang Shi

Received: 18 May 2011 / Accepted: 30 December 2011 / Published online: 11 January 2012

� Springer-Verlag 2012

Abstract

Purpose It is to compare the thermal damage on myo-

metrium tissue caused by five electrosurgical instruments,

including monopolar forceps, bipolar forceps, PK scalpel,

Ligasure and BiClamp.

Methods Normal myometrium in vitro was collected and

electric coagulation was conducted with five electrosurgi-

cal instruments under corresponding powers. The zones of

thermal injury (ZTI) in each coagulation sites were

examined histologically, while the width and depth of

thermal damage were measured.

Results 1. There were significant differences among vari-

ous groups’ widths of ZTI of myometrium (P \ 0.05). Lig-

asure produced the greatest width of ZTI, and it was

statistically greater than that of PK scalpel and BiClamp

(P \ 0.05). While the widths of ZTI caused by monopolar

and bipolar electrocoagulation lied between that of Ligasure

and PK scalpel, but the differences were of no statistical

significance (P [ 0.05). 2. The depths of ZTI in different

groups were of significant differences (P \ 0.05). Both

monopolar and bipolar forceps had greater depths of ZTI

compared with BiClamp (P \ 0.05) but not had statistical

differences with Ligasure and PK scalpel (P [ 0.05).

Conclusions As for myometrium, the thermal damage is

rather small in the horizontal and vertical directions when

using BiClamp and PK scalpel. Ligasure places larger

range of thermal damage in horizontal direction with little

depth in vertical direction, which is rather safe when acting

on uterine surface. Electrocoagulation was conducted with

monopolar (the power is 55 W) and bipolar forceps (the

power is 40 W) continuously for 3 s, whose thermal

damage range is fairly safe to corpus uteri wall and fundus

uteri.

Keywords Laparoscope � Electrosurgery �Thermal injury

Introduction

On the basis of minimal invasion and high efficiency, lap-

aroscopy has been extensively applied in gynecologic sur-

geries, especially prevailing in the surgery of uterine

fibroids, adenomyoma and other benign lesions, which

obviously benefits from reduction of intraoperative blood

loss, shortened operation time and increased operation

volume. However, the surgery-related complications caused

by various electrosurgical instruments are seldom, involv-

ing intraoperative uterine perforation, postoperative met-

roperitoneal fistula, hysterorrhexis during pregnancy [1–3],

and even some cases of hysterorrhexis during pregnancy

after the enucleation of subserous myoma of uterus [4].

Apart from specified surgical skills, the irrational use of

electrosurgical instruments incurring acute thermal damage

and secondary inflammatory reaction usually risk severe

surgical complications.

Thus, how to identify the optimal one from a large

number of electrosurgical instruments, particularly newly

Q. Zhu � J. Ruan � H. Liu � G. Shi (&)

Department of Obstetrics and Gynecology, West China

Second University Hospital, Sichuan University,

Chengdu 610041, China

e-mail: hxgangshi@163.com

L. Zhang

The First People’s Hospital of Chengdu, Chengdu,

Sichuan, China

W. Jiang

Department of Pathology, West China Second University

Hospital, Sichuan University, Chengdu 610041, China

123

Arch Gynecol Obstet (2012) 285:1637–1641

DOI 10.1007/s00404-011-2207-0

merged surgical instruments, is strongly required, when

coping with different surgical conditions. However, there are

no reports available to rely on in comparing thermal effects

and damages of uterine tissues caused by different electro-

surgical instruments. This presented study is designed to

compare the thermal damages caused by five common

electrosurgical instruments which act on myometrium tis-

sues, to identify the degree of thermal damage, as well as

providing evidence for the reasonable, high-efficient and

safe clinical use of various electrosurgical instruments.

Materials and methods

Surgical instruments

Following were the surgical instruments used: monopolar

and bipolar curved forceps, Stryker, USA; Gyrus Medical’s

PlasmakineticTM Tissue Management System, Gyrus

Medical’s, GER; closing forceps with 10 mm diameter of

LigasureTM Vessel Sealing System, Valleylab, USA;

VIO300D electrosurgery station BiClamp forceps, ERBE,

GER.

Specimens

Fifteen cases of women in child-bearing period, who had

been conducted hysterectomy because of hysteromyoma,

were brought into, whose normal muscle tissues of uterine

anterior and posterior wall were taken; women who were in

menopause, with complication of adenomyosis and uterine

cancer were excluded, nor the parts which are meaningful

for pathological diagnosis. The study proposal was

approved by the ethical committee of hospital. The study

was explained to all enrolled subjects, and a written

informed consent was obtained from each participant.

Experimental methods

Myometrium tissues were cut into 2 cm 9 2 cm 9 1 cm

tissue blocks, which were randomly distributed to be

appropriately experimentally treated. The distances

between forceps of instruments’ acting on tissues were all

set to be 5 mm, being measured by vernier caliper and

acting sites were marked by prepared Chinese ink. Based

on both the recommended power from the manufacturer’s

specifications and practical clinical application, monopolar

forceps (the electric coagulation power was 55 W) and

bipolar forceps (the electric coagulation power was 40 W)

were set to continuously coagulate for 3 s. The acting

time of PK scalpel (the power was automatically regulated

and controlled), Ligasure (conventional output parameters

of host was regulated to 2–3) and BiClamp forceps (effect

parameter was set to be 1) were regulated and controlled

by intelligent instruments.

The experiments were conducted by the same conduc-

tor, keeping constant contact pressure. After processing,

tissues were maintained at an extended state and were

placed in 10% formalin for fixed conservation. The time

interval from the isolation of all tissues to fixed conser-

vation was controlled to be in 2 h.

After the above processes, tissues were cut off passing

action spots and the section was perpendicular to wound

plane. Then the section was downward and paraffin-

embedded, sliced by 5 lm on section. Conventional HE

staining was carried out.

Outcome measures

Blind trial was adopted to observe pathological sections,

which was conducted by the same pathologist. Optical

microscope with standard micrometer was used to observe

the histopathological changes and measure the scope of

irreversible thermal damage, while the measurement was

accurate to 0.01 mm. Measurement indexes included: (1)

the horizontal width of the zones of thermal injury (ZTI) of

myometrium: the maximum horizontal diameter of damage

zone as the action spot is the center; (2) the vertical depth

of ZTI of myometrium: the maximum radial line which is

vertical to the surface of damage zone.

Statistical methods

Statistical analysis was performed using the SPSS� version

16.0 (SPSS, Chicago, IL). The measurement data are all

showed by �x� s. General Linear Model multivariate

analysis of variance is adopted to compare two sample

means of multi groups and further pairwise comparisons

are inspected by LSD. P = 0.05 (two-sided) was consid-

ered as the limit of significance.

Results

Histopathological features of thermal damage

in myometrium tissues

The morphological changes of thermal damage caused by

different instruments are all acute heat coagulable

necrosis. Under the microscope, membrane of smooth

muscle cells in ZTI disappeared, and endochylema was

homogeneous and concentrated red dyed. Crenas were

scattered in ZTI; nuclear chromatin was darkly stained,

and many nuclei became long flocculent or pyknosis.

In serious denaturation areas, cytoarchitecture could be

seen disappeared, and the whole showed homogeneous

1638 Arch Gynecol Obstet (2012) 285:1637–1641

123

and flake-like, while karyorrhexis and karyolysis were

visible.

The measured parameters of thermal damage in myo-

metrium tissues show that the maximum mean width was

produced by Ligasure, while the maximum mean depth was

caused by monopolar electrocoagulation. The measurement

results of different groups’ thermal damage scopes of

myometrium tissues are shown in Table 1.

Comparison of ZTI width

The comparison of ZTI width of different groups shows an

obvious difference (F = 141.902, P = 0.000), in which

Ligasure group’s thermal damage width is bigger than that

of PK scalpel group, BiClamp group (P \ 0.05), whilst

monopolar and bipolar electrocoagulation group are com-

parable (P [ 0.05) (Fig. 1).

Comparison of ZTI depth

There are differences among the comparison of damage

zones’ depth of myometrium (F = 34.586, P = 0.000),

among which, the depth of ZTI of monopolar electroco-

agulation group and bipolar electrocoagulation group are

greater than that of BiClamp group, and the difference is of

statistical significance (P \ 0.05). Other pairwise com-

parison differences are of no statistical significance

(P [ 0.05) (Fig. 2).

Discussion

Monopolar and bipolar forceps are frequently used

electrosurgical instruments in laparoscopic surgery. Sur-

geons always judge the degree of tissues’ thermal dam-

age according to its blanching, crenation, stiffening and

other manifestations, but cannot accurately estimate tis-

sues’ in-depth thermal damage range. The power and

process time of monopolar and bipolar forceps vary in

different literatures. According to the manufacturer’s

instructions, the recommended electric coagulation power

of monopolar and bipolar forceps was 30–70 W in

general surgery. Furthermore, it is frequently observed in

clinical practice and our previous study that excellent

hemostatic effect was always obtained through mono-

polar (55 W) and bipolar (40 W) forceps’ continuous 3-s

electrocoagulation. On this basis, we found that mono-

polar and bipolar forceps’ thermal damage depths in

vertical direction are remarkably more than the other

three instruments. When it has to be used, the surgeon

needs to be alert so as to avoid complications because

the thermal damage caused by the tip of forceps in

vertical direction may affect neighboring important tis-

sues. While in horizontal direction, the width of thermal

damage caused by monopolar and bipolar forceps is

smaller than that of Ligasure, but the difference is

without statistical significance. It is analyzed to be

connected with the Ligasure’s longer acting time and

Table 1 The width and depth

of ZTI of myometrium (�x� s)Groups Cases of tissues (n) Width (mm) Depth (mm)

Monopolar electrocoagulation group (ME) 9 4.57 ± 0.65 2.79 ± 1.11

Bipolar electrocoagulation group (BE) 10 4.29 ± 1.02 2.67 ± 1.26

PK scalpel group (PK) 10 3.90 ± 1.05 1.77 ± 0.95

Ligasure group (LS) 8 5.08 ± 1.28 2.16 ± 1.37

BiClamp forceps group (BC) 7 3.82 ± 1.39 1.49 ± 0.95

4.574.29

3.9

5.08

3.82

0

1

2

3

4

5

6

ME BE PK LS BC

wid

th m

eans

of Z

TI(

mm

)

ME

BE

PK

LS

BC

Fig. 1 The histogram of width means of ZTI of myometrium

2.792.67

1.77

2.16

1.49

0

0.5

1

1.5

2

2.5

3

ME BE PK LS BC

dept

h m

eans

of Z

TI(

mm

)

ME

BE

PK

LS

BC

Fig. 2 The histogram of depth means of ZTI of myometrium

Arch Gynecol Obstet (2012) 285:1637–1641 1639

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greater power output. Compared with conventional

bipolar electrocoagulation, Ligasure’s major function can

automatically adjust the output of power according to the

clamped tissues’ thickness or density, and close the

blood vessels, ligaments and tissue bundles that are

smaller than 7 mm, whose zonula occludens can bear

three times of normal human systolic blood pressure. It

is proved by experiments that this permanently closed

zonula occludens fibrosis can withstand the tension up to

900 mmHg, as same as that of ligation and vessel clamp

which are remarkably higher than that of Harmonic

scalpel and conventional bipolar electrocoagulation

[5–7]. When the power of high-frequency electric scalpel

is set, it will not vary with the changes of tissue

impedance, and its durative action may increase tissue

temperature markedly. Carbonization occurs, and it is

inseparably adhered with electrodes, so that it is easy to

tear eschar down, resulting in the bleeding of the he-

mostatic sites again. Therefore, for monopolar and

bipolar forceps, to achieve the same hemostatic effect as

Ligasure, acting time should be lengthened or electro-

coagulation repeated. But researches have shown that

heat energy produced by high-frequency electric current

is in direct proportion to acting time. With the length-

ening of cumulative acting time, the extent of thermal

damage extends outward [8]. Hence, when using mono-

polar and bipolar forceps, the electric coagulation should

be strictly controlled. Based on the previous studies on

the thermal effect caused by monopolar and bipolar

electric scalpels’ electrocoagulation, it has been indicated

that the unexpected surrounding thermal necrosis of

bipolar electric coagulation, involving bladder, ureter,

rectum and many other tissues, is less than that of

monopolar electric coagulation [9, 10]. The finding in

this study is consistent with others. However, the extent

of thermal damage between monopolar and bipolar are

similar, which may be related with the short acting time

set in this research and rather great tissue resistance,

which generates smaller thermal damage.

By means of real time detection of tissues’ resistance or

the current changes of power supply, smart bipolar system

feeds back to control components, to regulate the output

power for achieving better effect. Currently, the working

principles of the clinically frequently used PK scalpel,

Ligasure and BiClamp are similar, which can automatically

regulate output power and acting time. This research

indicates that Ligasure’s thermal damage width and depth

are greater than that of PK scalpel and BiClamp. After

analyzing the reasons, it owes to the various output powers

of different instruments, so that their effects are varied.

Tansatit et al. [11] found that the average burst pressure of

closing carotid of fresh body by Ligasure is higher than that

of BiClamp, and before the acting sites are completely

dried, BiClamp has automatically stopped energy output,

which indicates that its solidification effect of blood vessel

is worse than Ligasure. Oussoultzoglou et al. conducted

perspective study on the severity of hypocalcemia after

total thyroidectomy, then they found that the postoperative

severity of hypocalcemia of the patients who were operated

with BiClamp was lighter than who were with Ligasure

[12]. It indirectly suggests that BiClamp has less output

energy and smaller thermal damage range, which is con-

sistent with this research results. In the animal experiments

carried out by Carbonell et al., the burst pressure of Lig-

asure’s closing 2–3 mm diameter vessels was indifferent

from that of PK scalpel, but obviously higher when refer-

ring to 4–7 mm vessels. It implies that the hemostatic

effect of PK scalpel is weaker than Ligasure for the vessels

whose diameters are [3 mm [13]. In this research, the

thermal damage ranges of PK scalpel and BiClamp in

horizontal and vertical directions are rather small and

advantageous in safety, but the differences of its hemostatic

effect with Ligasure require further study.

Uterus is a muscular organ with cavity and thick wall,

whose different parts own varied thickness. When judging

the damage degree of myometrium in laparoscopic surgery,

it should be considered by combining uterine morphology.

Some scholars put forward that the depth of thermal

necrosis is inadvisable to exceed 20% of myometrium

thickness in uterine electrosurgery [14]. Duffy et al. [15]

measured the thickness of uterine wall during in vitro

experiments, acquiring that the average thickness of fundus

uteri was 1.4 cm, corpus uteri antetheca 1.8 cm, paries

posterior 1.9 cm, isthmus 1.3 cm, while the thinnest part

was just 0.7 cm, and the average thickness of cornua uteri

which was 0.5 cm from the entrance of oviduct was

0.6 cm. With the results of this study, we deduce that

monopolar forceps whose power is set to be 55 W and

bipolar clamp whose power is set to be 40 W continuously

electric coagulate for 3 s, while PK scalpel, Ligasure and

BiClamp are used under recommended setting, of which

the thermal damage range is relatively safe to uterine wall

and fundus uteri but beyond security scope when applied in

isthmus and cornua uteri. Cobellis enrolled 15 women who

underwent uterine myomectomy previously, and observed

uterine scar in the cesarean section. It was found that most

of the scars’ thickness of abdominal incision cases was in

accordance with the surrounding tissues. The scars of those

who had been conducted laparoscopic surgery possess

great tension and uneven edges, being thinner than the

surrounding tissues [16]. The structure of scar tissues dif-

fers from myometrium, without effective extention during

pregnancy. There is the risk of hysterorrhexis. Therefore,

when operating on the uterus of those who desires for

fertility, the time of electrocoagulation should be

strictly controlled, avoiding excessive coagulation. It is

1640 Arch Gynecol Obstet (2012) 285:1637–1641

123

noteworthy that the widths of ZTI are greater than the

depths, so what should be prevented is repeated or con-

tinuous electrocoagulating on section of myomectomy,

precluding that thermal damage exceeds security scope or

even extends through the full thickness of uterine wall.

Conclusion

The current finding suggests the use of BiClamp and PK

scalpel in uterine involved laparoscopy, especially for

those fertility conserved surgery, due to its relatively small

thermal damage on uterine tissues both in horizontal and

vertical directions. Ligasure’s thermal damage affects more

widely in horizontal direction but with very small depth

vertically, which is comparatively safe for superficial per-

formance on uterus, e.g. removal of subserous myoma.

Monopolar (the power is 55 W) and bipolar forceps (the

power is 40 W) continuously electrocoagulate for 3 s, as

well as PK scalpel, Ligasure and BiClamp, are relatively

safe when coping with uterine wall and fundus. However,

they may be at risk when acting on uterine isthmus and

cornua.

In this study, with certain power setting, the various

thermal damages on myometrium led by five common

electrosurgical instruments were outlined through a histo-

logical way. In brief, our findings provide evidence for

gynecologists to choose appropriate instruments in various

uterine laparoscopy. Nevertheless, there is limitation in this

study because of ex vivo tissue lack of blood supply, which

may not accurately reflect the in vivo situation. Further

research is needed in the thermal damage caused by the

same instrument under different powers and different act-

ing time.

Conflict of interest None.

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